Resolve "Operation Replacement in a SFG"

Added method with tests for replacing multiple operations in a sfg with another operation with the same amount of input / output ports. Closes #17

test/test_sfg.py

 import pytest
 
-from b_asic import SFG, Signal, Input, Output, Constant, Addition, Multiplication
+from b_asic import SFG, Signal, Input, Output, Constant, Addition, Subtraction, Multiplication, MAD, ConstantMultiplication, Butterfly
 
 
 class TestInit:
@@ -254,3 +254,42 @@ class TestReplaceComponents:
             assert True
         else:
             assert False
+
+class TestReplaceOperations:
+    def test_replace_mul_add_with_mad(self):
+        in1 = Input()
+        in2 = Input()
+        in3 = Input()
+        mul1 = in1 * in2
+        add1 = mul1 + in3
+        out1 = Output(add1)
+        sfg = SFG(inputs=[in1, in2, in3], outputs=[out1])
+
+        mad1 = MAD()
+        _sfg = sfg.replace_operations(['add1', 'mul1'], mad1)
+
+        assert 'mad1' in _sfg._components_by_id.keys()
+        assert {add1, mul1} not in _sfg.operations
+        assert _sfg.input(0).signals
+
+    def test_replace_neg_add_with_sub(self):
+        in1 = Input()
+        in2 = Input()
+        neg1 = ConstantMultiplication(-1, in1)
+        add1 = neg1 + in2
+        out1 = Output(add1)
+        sfg = SFG(inputs=[in1, in2], outputs=[out1])
+
+        sub1 = Subtraction()
+        _sfg = sfg.replace_operations(['add1', 'cmul1'], sub1)
+
+        assert 'sub1' in _sfg._components_by_id.keys()
+        assert {add1, neg1} not in _sfg.operations
+        assert _sfg.input(0).signals
+
+    def test_different_input_output_count(self, operation_tree):
+        sfg = SFG(outputs=[Output(operation_tree)])
+
+        constmul1 = ConstantMultiplication()
+        with pytest.raises(AssertionError):
+            sfg.replace_operations(['add1'], constmul1)

[Angus Lothian]

Test case requires more asserts that ensure that the resulting SFG has the connections right and that the MAD is in the right place of the SFG.

[Angus Lothian]

More asserts same as previous comment.